1. Field of the Invention
The present invention relates, in general, to a data output buffer for amplifying data read from a semiconductor memory device and transferring the amplified data to the peripheral circuit, and more particularly, to a mode adaptive data output buffer for a semiconductor memory device which is capable of performing a high-speed operation and minimizing the generation of noise regardless of a data mode.
2. Description of the Prior Art
Generally, a semiconductor memory device such as a dynamic random access memory or a static random access memory comprises a data output buffer for amplifying data read from a memory cell so that it can have a voltage level required by the peripheral circuit. The data output buffer can generate output data (referred to hereinafter as "2-level data"), which has a voltage level Vcc of high logic and a voltage level Vss of low logic. Alternatively, the data output buffer can generate output data (referred to hereinafter as "3-level data"), which varies with the voltage level Vss of low logic and the voltage level Vcc of high logic on the basis of a voltage level (about 1.4 V) of high impedance state which is a reference level.
Such a conventional data output buffer may employ a circuit device with a large current amount, to enhance the operation speed. In this case, the conventional data output buffer generates 3-level data which has little noise at its edge portion. However, the conventional data output buffer generates 2-level data, which has excessive noise at its edge portion. Such excessive noise results in a degradation of the response speed of output data with respect to input data. The reason is that the 2-level data has a wider swing width whereas the 3-level data has a narrower swing width.
The conventional data output buffer may employ a circuit device with a small current amount to minimize the generation of noise at the edge portion of the 2-level data. In this case, the response speed of the 3-level data with respect to input data is significantly degraded.
As mentioned above, the conventional data output buffer has the disadvantage that the operation speed is degraded and the noise component is increased, according to the output data mode.